General Background
Pain and overuse disorders of the joints of the body is a common problem. For instance, one of the most important joints which are liable to wearing and disease is the knee. The knee provides support and mobility and is the largest and strongest joint in the body. Pain in the knee can be caused by for example injury, arthritis or infection. The weight-bearing and articulating surfaces of the knees, and of other joints, are covered with a layer of soft tissue that typically comprises a significant amount of hyaline cartilage. The friction between the cartilage and the surrounding parts of the joint is very low, which facilitates movement of the joints under high pressure. The cartilage is however prone to damage due to disease, injury or chronic wear. Moreover it does not readily heal after damages, as opposed to other connective tissue, and if healed the durable hyaline cartilage is often replaced by less durable fibrocartilage. This means that damages of the cartilage gradually become worse. Along with injury/disease comes a problem with pain which results in handicap and loss of function. It is therefore important to have efficient means and methods for repairing damaged cartilage in knee joints.
Today's knee prostheses are successful in relieving pain but there is a limit in the lifetime of the prostheses of 10-15 years. The surgical operation is demanding and the convalescence time is often around 6-12 months. In many cases today, surgery is avoided if training and painkillers can reduce the pain. Prostheses are therefore foremost for elderly patients in great pain, at the end of the disease process; a totally destroyed joint. There are different kinds of prostheses, such as half prosthesis, total prosthesis and revision knee, the latter used after a prosthesis failure. The materials used in today's knee prostheses are often a combination of a metal and a polymeric material, but other materials such as ceramics have also been used. The size of knee prostheses makes it necessary to insert them through open surgery.
Other attempts practiced at various clinics around the world with the main objective to repair or rebuild cartilage include biological approaches such as micro fractures, cartilage cell transplantation (ACI), periost flap, and mosaic plasty surgery. In mosaicplasty surgery grafts, in the form of plugs or dowels of healthy cartilage and underlying bone are harvested from nonbearing parts of the join, i.e areas of low stress in the joint. Such plugs may be denoted osteochondral plugs. In related surgical techniques similarly shaped plugs as those of mosaicplasty, but made of artificial material, may be used. The plugs or dowels are inserted into drill holes made at the diseased or damaged site, such that they form a mosaic pattern of healthy cartilage at the surface of the joint. Osteochondral autograft transfer (OATS) is a technique similar to mosaicplasty but during the OATS procedure the plugs are usually larger, and therefore only one or two plugs are needed to fill the area of cartilage damage. A difficulty with both mosaicplasty and OATS is to make sure that the plugs are inserted such that they form an even surface. If the plugs are offset from their intended position, e.g. such that they are tilted or project over the surrounding cartilage tissue, it may cause increased wear and load on the joint, resulting in more pain for the patient. The biological treatments have shown only limited results this far, with implications such as high cost, risk of infection, risk of loosening, limited suitability for patients of different ages and the extent and location of damage. They do however have many advantages, especially for young patients who still are growing and who have better abilities for self-repair, if these difficulties can be overcome.
The advantages of implants have stimulated a further development of smaller implants that can be implanted with less invasive surgery. In this development there has also been an effort to achieve small joint implants, suitable for repair of a small cartilage injury that have a minimal influence on the surrounding parts of the joint. In the current development, such small implants are designed with an implant body that may be formed as a thin plate with a hard surface for facing the articulate side of the joint and a bone contacting surface for facing the bone below the damaged part of cartilage. The shape and the curvature of the articulate surface of the implant may be designed to be similar to the shape and the curvature of the part of the joint where the implant is inserted. Such implants are designed as mushrooms with an implant body or head and optionally with a peg or a rod projecting from the bone contacting side of the implant body for fastening the implant to the bone.
In the surgical operation of implanting small implants, including grafted plugs or artificial plugs used for mosaicplasty or OATS, it is critical that the implant is positioned in a precise manner. If the implant is offset from its intended position it may cause increased wear or load on the joint. For example, if the implant is tilted this may result in an edge that projects above the cartilage surface and causes wear on the opposing cartilage in the joint. Another example is when the implant is placed in a position with the surface of the implant projecting above the surface of the cartilage causing the joint to articulate in an uneven manner and increasing the load on an opposing point of the joint. For the patient, also small misplacements or deviations from an ideal position may result in pain, longer time for convalescence or even a surgical operation being done in vain and making it more difficult to repair the damage in the joint. A large burden is therefore placed on the surgeon not to misplace or misfit the implant. In order to support the surgeon during the implant surgery and to improve the positioning of the implant various tools and guides that support the surgical procedure have been developed.
Specific Background
During cartilage repair in a joint, different methods are known today for repair of cartilage damages. One example is replacing damaged cartilage and thereby repairing a part, namely the damaged part, of the cartilage in the joint instead of replacing the whole joint. This method, replacing a part of the cartilage in the joint using an implant, requires high precision tools. During such a repair it is important that the replacement is well fitted in the joint otherwise the implant will start to move and the repair in the joint will not last for long. The instruments on the market today are not user friendly and require much skills of the surgeon. Several instruments are needed for forming a recess for an implant and may lead to that there is lack of fit for the implant due to the several steps needed for making a recess. There is a need for improved instrumentation during these sorts of cartilage repairs. Improved instrumentation which is easy to use, and which gives the same result without dependence on which surgeon who is using them. It is also important that the instruments allow for short implantation procedures.
Some of the surgical tools developed for implant surgery include guide tools having a channel or similar through which the surgical tools and/or the implant are guided throughout the surgery. Often these guide tools are rather bulky and placed over the damaged site of the cartilage such that it is difficult for the surgeon to see the site of implantation during surgery. Also it may be difficult to remove debris and waste that is generated at the implantation site during surgery. In order for the surgeon to be able to inspect the implantation site and/or remove such surgery the guide tool has to be removed from the surgical site in the joint. There is a need for a surgical kit for replacement or repair of damaged cartilage at an articular surface in a joint that guides the surgeon, improves the positioning of the implant or the grated or artificial plugs used for mosaicplasty or OATS, and that facilitates inspection of the implantation site and removal of debris during surgery.
Prior Art
Examples of prior art disclosing smaller implants and tools for replacement of damaged cartilage are shown in:
WO2007/014164 A2 describes a kit comprising a plurality of small joint implants having different predetermined shapes described as circular, oval, L-shaped and triangular and tools for placing the implants and a method for placing the implant in a joint, e.g. in the knee or other joints where there is a need for repair of a cartilage and/or bone damage. In this piece of prior art each implant shape has a specific guide tool which corresponds to the shape of the implant.
The cartilage damage is repaired by choosing the most suitable implant from the different shapes mentioned above. The corresponding guide tool is selected and is used for faster reaming of the area where the implant is to be placed. A drill is used for drilling a hole to accept the post extending from the bone contacting side of the implant. In the end, the implant is placed on the area reamed or drilled out for the implant. Although it is the intention that the guide tool shall be used for the preparation of the placement of the implant it is also said that the use of the guide tool is optional, see passage sections [019, 020].
US20030216669 A1 Shows methods and compositions for producing articular repair material used for repairing an articular surface. The method for designing an articular implant comprises; taking an image of the joint, reconstructing dimensions of the diseased cartilage surface to correspond to normal cartilage and designing the medical implant accordingly. This prior art also shows a surgical assistance device or surgical tool for preparing the joint to receive an implant. The surgical tool comprises of one or more surfaces or members that conform to the shape of the articular surfaces of the joint. It can include apertures, slots and/or holes that can accommodate surgical instruments such as drills and saws. (see claim 18, [0029], [175] FIG. 13, 15, 16), and thus may also be designed and used to control drill alignment, depth and width, for example when preparing a site to receive an implant [0179]. The tool may be single-use or reusable [181]. These surgical tools (devices) can also be used to remove an area of diseased cartilage and underlying bone or an area slightly larger than the diseased cartilage and underlying bone [0182].
EP 1 698 307 A1 discloses an instrument for removing cartilage and introducing an implantable nonwowen into cartilage. The instrument may further comprise a cartilage puncher having a channel through which further instruments, such as surgical spoons or curettes, can be guided to the cartilage defect ([0028-0029]).
WO2008098061 A2 also shows examples of small articular surface implants and tools for placement of the implants. The tools and the implant are used to repair damaged articular cartilage areas.
WO2006091686 A2 Shows a small implant for replacing a portion of an articular surface (see the abstract). The implant is placed using a rotating excision tool (see page 8 line 25) and the implant is selected from a set (see page 10 line 22-23).
WO 2009111626 Shows implants for altering wear patterns of articular surfaces of joints (see [00190]) and a device and a method for repair of articular surfaces, in for example a knee. The implants and methods may replace all or a portion of the articular surface and achieve an anatomic or near anatomic fit with the surrounding structures and tissues, the techniques described herein allow for the customization of the implant to suit a particular subject, the implant is a mirror image of the articular surface, see[0057]-[0058]. The implants are selected from predetermined shaped and their location can be optimized for the patients wear pattern and the wear patterns are assessed by for example MRI [0061]-[0063], [0072]. The tools used for placement of the implants are selected depending on MRI images but not created depending on the images [00211].
WO2008101090 A2 shows a method for making a large implant suitable for a joint. The 3D surface of the joint implant is determined using MRI or CT depicting the damaged that is to be repaired.
US2006/0198877 A1 shows a medical instrument for autologous chondrocyte transplantation.
WO2009/108591 A1 shows a method and tools for repairing an articular cartilage defect and also an implant.
U.S. Pat. No. 6,306,142B1 shows a system and tools for transplanting a bone plug from a donor site to a recipient site.
US 2003/0100947 A1 shows a device for repairing articular cartilage defects.
EP2389905B1 describes a method for designing a surgical kit comprising a drill bit for drilling. Several instruments are needed for making the recess for an implant comprising an extending post.